1. Field of the Invention
The present invention relates to a method and apparatus of automatically identifying the species of coal (hereinafter referred to as "coal species"), i.e. discriminating a coal species from other coal species in a non-contact manner.
2. Description of the Prior Art
The property of coal varies according to its production area. The coal can be roughly classified into anthracite (hard coal), bituminous coal (soft coal), lignite (brawn coal). etc. on the basis of the property of coal. The coal was formed as a result that the fiber elements of plants stacked in the geological age were subjected to dehydrating reactions to be humificated. The humification degree of coal increases with advancement of the brawn coal, bituminous coal and anthracite. Correspondingly, the coal rank increases to have a tendency of the volatile component becoming small. In this way, the contents or component of the coal vary with the degree of humification. Thus, the many species of coal were born from various areas. However, conventionally, the property of the coal could not be precisely discriminated by color or smell. For this reason, the property obtained from the chemical analysis of components of the coal was compared with the past data of the property so that the coal species was discriminated from one another.
However, the chemical analysis requires a relatively long time (three or four days) and skill. The method using the chemical analysis was disadvantageous in a case where the coal species should be discriminated instantaneously, for example, the species of coal to be used as fuel in a fuel supply line for a boiler should be changed for combustion adjustment.
There was also an attempt of measuring the volatile component of coal using intermediate-infrared rays to automate and continue the quality control. However, this attempt was disadvantageous in discriminating the species/property of coal at great accuracy for the reasons: (1) the sensitivity of a detector is low because of using intermediate infrared rays, (2) weak reflected light due to strong absorption of water in an intermediate infrared region lowers the S/N ratio so that the discrimination accuracy is greatly affected by stray light, and (3) because the infrared rays due to the thermal radiation from a coal sample to be measured are radiated in the intermediate region, the identifying accuracy will be affected by the temperature of the coal sample.
Further, as the case may be, the coal species may be changed in a fuel supply line for e.g. a boiler. In this case, even if the property of coal can be discriminated, it was difficult to discriminate the coal species at issue from other coal species.